Printing device and method of manufacturing a light emitting device

ABSTRACT

A first pressure generating chamber, which is sealed by a first elastic plate mounted with a first piezoelectric element at one surface, and a second pressure generating chamber, which is sealed by a second elastic plate mounted with a second piezoelectric element at one surface are formed in a casing. The second pressure generating chamber is formed with an opening which is a discharge port. A mixture is discharged from the discharge port. A nozzle formed with an opening jets gas toward a substrate surface, and is provided in the vicinity of the discharge port of the ink head.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a lightemitting device which has a light emitting element in which an emittercomposed of an organic compound is provided between a pair ofelectrodes, and to a printing device which is applicable to themanufacture of the light emitting device.

2. Description of the Related Art

A light emitting element in which an organic compound is used for anemitter (hereinafter referred to as organic light emitting element)generally has a sandwich structure in which an organic compound layer isformed between a cathode and an anode. In case of using a low molecularweight organic compound, the structure is formed by combining layerssuch as a hole injecting layer, a hole transporting layer, a lightemitting layer, an electron transporting layer and an electron injectinglayer, which are composed of respective materials. The hole injectinglayer and the hole transporting layer are not necessarily strictlydistinguished, and the hole transporting property (hole mobility) is aparticularly important characteristic for both the layers. For the sakeof convenience, the hole injecting layer corresponds to a layer thatcontacts an anode, and a layer that contacts the hole injection layer iscalled the hole transporting layer. Thus, both the layers aredistinguished from each other. Also, a layer that contacts a cathode iscalled the electron injecting layer, and a layer that contacts theelectron injecting layer is called the electron transporting layer. Thelight emitting layer may also serve as the electron transporting layer,and thus, is also called a light emitting electron transporting layer. Avacuum evaporation method is adopted for forming a layer composed of thelow molecular weight organic compound.

On the contrary, a polymer organic compound material is formed by a wetmethod such as an application method or a printing method. Recently, anink jet printing method has attracted attention, and the technique isdisclosed in JP 10-12377 A, JP 10-153967 A, JP 11-54270 A, and the like.As the organic compound material used in the ink jet method, awater-soluble, or alcohol or glycol-soluble material is applied, and aprecursor of polyparaphenylene vinylene (hereinafter referred to as PPV)or the like is used therefor. The PPV precursor becomes salt anddissolves in water, and is polymerized to become a high polymer byheating after application.

A light emitting mechanism in the above-mentioned organic compounds isregarded as a phenomenon in which: an electron injected from a cathodeand a hole injected from an anode recombine in a light emitting layercomposed of an emitter to form a molecular exciton; and light is emitterwhen the molecular exciton returns to a base state. There are lightemission from a singlet excitation state (fluorescence) and lightemission from a triplet excitation state (phosphorescence). A luminanceranges from several thousands to several tens of thousands cd/m². Thus,it is considered that the light emitting mechanism can be sufficientlyapplied to a display device and the like in principle.

It is impossible in terms of heat-resistance or water-resistance that anorganic compound layer is formed by patterning with an exposure processlike semiconductor. The organic compound layer is formed by patterningwith a shadow mask in a vacuum evaporation method. In this case, anorganic compound material attached to the shadow mask is not utilizedand lost. Besides, the organic compound material that remains on aninner wall of a chamber of an evaporation device and in a crucible of anevaporation source becomes a loss. Thus, the utilization efficiency isexpected to be approximately 10%. Therefore, the low molecular weightorganic compound layer formed by the vacuum evaporation method hasinvolved a problem in that the utilization efficiency of the material ispoor.

Of course, it may be sufficient that the material cost is low. However,the low molecular weight organic compound material needed to have higherpurity is expensive, which is reflected in the cost of a product.

On the other hand, when an organic light emitting element is formed bythe ink jet method using a polymer organic compound, there is anadvantage that the patterning formation step is simple and easy. Anorganic compound layer is formed for each dot, whereby the steps such asphotoresist patterning and etching are not required. Further, theutilization efficiency of the material by far increases, and it becomespossible to secure the utilization efficiency of 80% or more.

However, as a multiple production method in which a plurality of displaypanels are taken out from one large-area substrate, it can not be saidthat the ink jet method in which a mixture is dropped each dot hasalways high capacity as an effective production method. The ink jetmethod has involved a problem in that a processing time increases afterall since higher accuracy of position and higher processing speed aredemanded as a screen size becomes larger and the number of pixelsincreases.

Further, in the case where the organic compound layer is formed bydropping the mixture every dot, variation in a discharge amount of themixture and fluctuation of a drop position lead to unevenness inemission intensity, which causes degradation of quality of a lightemitting device constituted of a large number of light emittingelements.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-describedproblems, and an object of the present invention is therefore to providea printing device which is capable of conducting formation of an organiccompound layer by an ink jet method in a simple and easy manner and athigh speed, and to provide a method of manufacturing a light emittingdevice using the printing device.

In order to solve the above-described problems, a printing deviceaccording to an aspect of the present invention is characterized in thestructure of an ink head and includes an ink head which has: a firstelastic plate mounted with a first piezoelectric element: a secondelastic plate mounted with a second piezoelectric element; a pressuregenerating chamber sealed by the first elastic plate at one surface; anda supply path connected with the pressure generating chamber and sealedby the second elastic plate at one surface, and means for leveling amixture discharged from the ink head by jet of gas, wherein the firstpiezoelectric element is operated at a higher oscillation frequency thanthat of the second piezoelectric element to continuously discharge themixture.

According to another aspect of the present invention, there is provideda printing device including an ink head which has: a first elastic platemounted with a first piezoelectric element; a second elastic platemounted with a second piezoelectric element; a pressure generatingchamber sealed by the first elastic plate at one surface: and a supplypath connected with the pressure generating chamber and sealed by thesecond elastic plate at one surface; and means for leveling a mixturedischarged from the ink head by jet of gas, wherein the device isprovided with a function of continuously discharging the mixture by thefirst elastic plate mounted with the first piezoelectric element andstopping the discharge of the mixture by the second elastic platemounted with the second piezoelectric element.

A solution in which an organic light emitting material or a precursorthereof is dissolved or dispersed in a liquid is used as the mixture.The mixture is discharged continuously, whereby the time for positioncontrol is shortened and the printing speed can be increased incomparison with an ink jet method in which ink is printed for each dot.In particular, the present invention is appropriately applied to aproduction method using mother glass, in which a plurality of displaypanels are taken out from a large-area substrate. Further, in the casewhere a plurality of pixel regions are provided in the mother glass, thedischarge of the mixture is stopped instantaneously during a movement ofthe ink head between the pixel re-ions, whereby the ink head can bemoved at higher speed to the mother glass. The second piezoelectricelement is provided in order to stop the discharge of the mixtureinstantaneously, whereby the high speed in printing can be realized.

A method of manufacturing a light emitting device, that uses the ink jetprinting, device with the above-described structure, includes: a firststage of forming a stripe-shaped organic compound layer in a pixelregion by continuously dropping a mixture from an ink head due tovibration of a first piezoelectric element; and a second stage ofstopping the vibration of the first piezoelectric element andinstantaneously stopping the drop of the mixture by a secondpiezoelectric element. In this case, a stripe-shaped organic compoundlayer may be formed in a pixel region by applying the mixture andspraying gas to the application surface for leveling of the surface.

Accordingly to another aspect of the present invention, there isprovided a method of manufacturing a light emitting device for formingan organic compound layer by an ink jet method on a substrate in whichfirst to n-th (n>1) pixel regions are defined, including: a first stageof forming a stripe-shaped organic compound layer in the first pixelregion by continuously dropping a mixture from an ink head due tovibration of a first piezoelectric element; and a second stage ofstopping the vibration of the first piezoelectric element,instantaneously stopping the drop of the mixture by a secondpiezoelectric element, and moving the ink head to the second pixelregion. In this way, stripe-shaped organic compound layers are formed inthe first to n-th pixel regions. Further, in this case as well, astripe-shaped organic compound layer may be formed in a pixel region byapplying the mixture and spraying a gas to the application surface forleveling of the surface

In the above-described method of manufacturing a light emitting device,a first organic compound layer may be formed by an application method,and then, a second organic compound layer may be formed by an ink jetprinting method. The first organic compound layer may be formed frompolyethylene dioxythiophene or the like.

The first and second piezoelectric elements are incorporated into theink head, and the timings for causing displacement are synchronized,whereby the mixture can be discharged continuously, or the discharge canbe stopped instantaneously. The mixture is discharged continuously toform an organic compound layer. Thus, the time for position control isshortened, and the printing speed can be increased in comparison with anink jet method in which ink is printed for each dot. In particular, thepresent invention is appropriately applied to a production method inwhich a plurality of display panels are taken out from a large-areasubstrate. Further, in the case where a plurality of pixel regions areprovided in the large-area substrate, the discharge of the mixture isstopped instantaneously during a movement of the ink head between thepixel regions, whereby the ink head can be moved at higher speed to thelarge-area substrate. The second piezoelectric element is provided inorder to stop the discharge of the mixture instantaneously. This meansis provided, whereby the high speed in printing can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a sectional view explaining a structure of an ink head of thepresent invention;

FIG. 2 is a sectional view explaining a structure of an ink head of thepresent invention;

FIGS. 3A and 3B are sectional views explaining structures and anoperation of the ink head of the present invention;

FIG. 4 is a diagram explaining an operation timing of a piezoelectricelement;

FIG. 5 is a diagram explaining a structure of an ink jet method printingdevice according to the present invention;

FIG. 6 is a diagram explaining a printing step of an organic compoundlayer to a substrate having a pixel region:

FIG. 7 is a diagram explaining a printing step of an organic compoundlayer to a substrate having a pixel region:

FIG. 8 is a diagram explaining a printing step of an organic compoundlayer to a substrate having a plurality of pixel regions;

FIG. 9 is a diagram showing an example of a manufacturing device forforming a light emitting device;

FIG. 10 is a diagram showing an example of a manufacturing device forforming a light emitting device:

FIG. 11 is a top view explaining a structure of a pixel of an organiclight emitting element;

FIG. 12 is a sectional view explaining the structure of the pixel of theorganic light emitting element;

FIGS. 13A and 13B are a top view and a sectional view showing astructure of a light emitting device, respectively;

FIGS. 14A and 14B are top views showing an embodiment in which anorganic compound layer is formed in a pixel region of an organic lightemitting element;

FIGS. 15A to 15F are diagrams showing examples of electronic deviceswhich are completed by using the light emitting device manufactured byusing the present invention; and

FIGS. 16A and 16B are diagrams showing examples of electronic deviceswhich are completed by using the light emitting device manufacturedusing the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment mode of the present invention is describedwith reference to the accompanying drawings. FIG. 5 shows a structure ofa printing device using an ink jet method according to the presentinvention. The printing device is constituted of an ink head 401, anozzle 403 for spraying gas, a stage 405 for fixing a substrate, and thelike. In addition, subordinate elements such as a cassette 407 forholding a substrate to be processed and a conveying means 406 forbringing in and carrying out the substrate from the cassette 407 may beprovided. A mixture is supplied to the ink head 401 from a reservoirtank 402. Further, the gas to be sprayed is supplied from a gas supplymeans 404 constituted of a compression container, a filter, a flowcontrol device, and the like. An inert gas is used as the gas, andnitrogen, argon or the like is applied thereto.

The nozzle 403 for spraying gas is provided adjacently to the ink head401. The gas sprayed from the nozzle is used for leveling the mixturedischarged onto a substrate 408.

Most of mixtures are easy to be oxidized. Thus, it is desirable that theinert gas such as nitrogen is supplied to the inside of a processingchamber 409 by a gas supply means 410 and that the atmosphere in theprocessing chamber 409 is substituted.

FIG. 1 is a sectional view of a structure of the ink head. In a casing101, a first pressure generating chamber 106 which is sealed by a firstelastic plate 103 mounted with a first piezoelectric element 102 at onesurface, and a second pressure generating chamber 107 which is sealed bya second elastic plate 105 mounted with a second piezoelectric element104, are formed. The second pressure generating chamber 107 is formedwith an opening, which is a discharge port 108 for discharging amixture. A nozzle 109 formed with an opening 110 jets a gas toward asubstrate surface, and is provided in the vicinity of the discharge port108 of the ink head.

The first elastic plate 103 constituting the first pressure generatingchamber 106 varies the volume of the first pressure generating chamber106 due to bending displacement of the first piezoelectric element 102to thereby discharge the mixture. On the other hand, the second elasticplate 105 of the second pressure generating chamber 107 also varies thevolume of the second pressure generating chamber 107 due to the bendingdisplacement of the second piezoelectric element 104 to thereby stop thedischarge of the mixture.

FIGS. 3A and 3B are diagrams explaining an operation for discharging themixture from the ink head. The volume of the first pressure generatingchamber 106 is varied due to vibration of the first piezoelectricelement 102 and the mixture is discharged from the discharge port 108through the second pressure generating chamber 107. Along with this, amixture 115 is supplied timely from a reservoir. At this time, thesecond piezoelectric element 104 does not vibrate but remains at a fixedposition. To stop the discharge of the mixture 120, the vibration of thefirst piezoelectric element 102 is stopped, and the second piezoelectricelement 104 of the second pressure generating chamber 107 is displacedso that the volume of the second pressure generating chamber 107 becomeslarger. With the displacement of the second piezoelectric element 104,the elastic plate 105 is displaced, and thus, the volume of the secondpressure generating chamber 107 can be made larger. Thus, the dischargeof the mixture can be instantaneously stopped.

FIG. 4 is a timing chart of a signal voltage applied to thepiezoelectric element. A pulse voltage is imparted to the firstpiezoelectric element in a short cycle, whereby the mixture iscontinuously discharged. The discharge is conducted for a predeterminedperiod, and the pulse voltage is stopped at the time of stopping thedischarge. At the same time, a pulse voltage is applied to the secondpiezoelectric element to cause displacement, and the discharge isinstantaneously stopped.

In this way, the two piezoelectric elements are incorporated into theink head, and the timings for causing displacement are synchronized asshown in FIG. 4, whereby the mixture can be discharged continuously, orthe discharge can be stopped instantaneously.

FIG. 2 shows another example of an ink head. This ink head has astructure in which a first piezoelectric element 202, a first elasticplate 203, a second piezoelectric element 204, and a second elasticplate 205 are provided in a casing 201, and the ink head can dischargethe mixture continuously or stop the discharge instantaneously as in theabove-described ink head. Note that the second piezoelectric element 204and the second elastic plate 205 are provided on the midway of a supplypath 211 that extends from a pressure generating chamber 207. Thisstructure has a mechanism in which the supply path 211 is closed due tothe displacement of the second piezoelectric element 204 to stop thedischarge of the mixture from a discharge port 108. In addition, anozzle 2109 for jetting gas has the same structure as that in FIG. 1.

One discharge port may be provided to the ink head. Also, a plurality ofdischarge ports may be provided in order to conduct printing moreeffectively. For example, a pair of pressure generating chambers and adischarge port may be provided as one pair. Also, a pair of pressuregenerating chambers may be provided to a plurality of discharge ports.

The first and second piezoelectric elements are incorporated into theink head, and the timings for causing displacement are synchronized,whereby the mixture can be discharged continuously, or the discharge canbe stopped instantaneously. As shown in FIG. 4, the first piezoelectricelement and the second piezoelectric element are synchronized to causethe mixture to be discharged continuously and form an organic compoundlayer. Thus, time for position control is shortened, and the printingspeed can be increased. In particular, the present invention isappropriately applied to a production method in which a plurality ofdisplay panels are taken out from a large-area substrate. Further, inthe case where a plurality of pixel regions are provided in thelarge-area substrate, the discharge of the mixture is stoppedinstantaneously during a movement of the ink head between the pixelregions, whereby the ink head can be moved at higher speed to thelarge-area substrate. The second piezoelectric element is provided inorder to stop the discharge of the mixture instantaneously, whereby thehigh speed in printing can be realized.

Embodiment 1

FIG. 6 schematically shows a state that a polymer organic compound layeris formed so as to match with a pixel region on a substrate in which oneelectrode of an organic light emitting element by using an ink jetprinting device according to the present invention. In FIG. 6, referencenumeral 610 indicates a substrate, and a pixel region 611, a source sidedriver circuit 612 and a gate side driver circuit 613 are formed byusing TFTs on the substrate 610. The pixel region corresponds to theregion surrounded by a plurality of source wirings connected to thesource side driver circuit 612 and a plurality of gate wirings connectedto the gate side driver circuit 613. A TFT and an organic light emittingelement electrically connected with the, TFT are formed in the pixelregion. The pixel region 611 is defined as the above-described region inwhich pixels are arranged in matrix.

Here, reference symbol 614 a indicates a mixture of an organic compoundmaterial for emitting red light and a solvent (hereinafter, referred toas mixture for a red light emitting layer), reference symbol 614 bindicates a mixture of an organic compound material for emitting greenlight and a solvent (hereinafter, referred to as mixture for a greenlight emitting layer), and reference numeral 614 c indicates a mixtureof an organic compound material for emitting blue light and a solvent(hereinafter, referred to as mixture for a blue light emitting layer).Incidentally, there are given two methods: a method in which apolymerized polymer organic compound material is directly dissolved in asolvent for application; and a method in which a precursor dissolved ina solvent is deposited into a film and then the film is subjected tothermal polymerization. Both the methods may be adopted.

The mixture for a red light emitting layer 614 a, the mixture for agreen light emitting layer 614 b, and the mixture for a blue lightemitting layer 614 c are separately discharged from an ink head, and areapplied in a direction indicated by an arrow. That is, stripe-shapedlight emitting layers are formed simultaneously for organic compoundlayers for emitting red light; organic compound layers for emittinggreen light; and organic compound layers for emitting blue light.

As the polymer organic compound for forming the organic compound layer,a substance which is soluble in an organic solvent, such as apolyparaphenylene vinylene derivative, a polythiophene derivative, apolyfluorene derivative, a polyparaphenylene derivative, apolyalkylphenylene derivative or a polyacetylene derivative, can beused.

As the polyparaphenylene vinylene derivative,poly(2,5-dialkoxy-1,4-phenylenevinylene): RO—PPV can be used.Specifically, materials such aspoly(2-methoxy-5-(2-ethyl-hexoxy)-1,4-phenylenevinylene): MEH-PPV andpoly(2,5-dimethyloctylsilyl-1,4-phenylenevinylene): DMOS—PPV can beused.

As the polyparaphenylene derivative, poly(2,5-dialkoxy-1,4-phenylene):RO—PPP can be used.

As the polythiophene derivative, poly(3-alkylthiophene): PAT can beused. Specifically, materials such as poly(3-hexylthiophene): PHT,poly(3-cyclohexylthiophene): PCHT can be used. In addition,poly(3-cyclohexyl-4-methylthiophene): PCHMT,poly(3-[4-octylphenyl]2,2′bithiophene): PTOPT,poly(3-(4-octylphenyl)-thiophene): POPT-1 and the like can be used.

As the polyfluorene derivative, poly(dialkylfluorene): PDAF can be used.Specifically, materials such as poly(dioctylfluorene): PODF can be used.

As the polyacetylene derivative, materials such aspolypropylphenylacetylene: PPA-iPr, polybutylphenylphenylacetylene:PDPA-nBu, and polyhexylphenylacetylene: PHPA can be used.

Further, examples of a solvent for the above polymer organic compoundinclude toluene, benzene, chlorobenzene, dichlorobenzene, chloroform,tetralin, xylene, anisole, dichloromethane, a-butyrolactone,butylcellosolve, cyclohexane. NMP (N-methyl-2-pyrrolidone), dimethylsulfoxide, cyclohexanone, dioxane and THF (tetrahydrofuran).

Further, PEDOT (poly(3,4-ethylene dioxythiophene)) or polyaniline (PA)can be used as a hole injecting polymer compound. Incidentally, thesematerials are water-soluble. The PEDOT can also be formed by anapplication method. A first organic compound layer (PEDOT) may be formedby the application method, and then, a second organic compound layer maybe formed on the first organic compound layer by an ink jet method.

In addition, an aggregate of an organic compound which does not havesubliming property or dissolving property (preferably, an aggregatewhich has molecularity of 10 or less), or an organic compound (referredto as intermediate molecular weight organic compound) which has amolecular chain length of 5 μm or less (preferably 50 nm or less) can beused. An example of such a material istetrakis(2-mercapto-benzoxazolate)tungsten. In pattern formation by anink jet method using a polymer organic compound material, there is aproblem that a dropped mixture becomes a linear shape like a thread.However, such a defect is not caused in the intermediate molecularweight organic compound in which the number of chain molecules is small.In the case of forming the mixture of the polymer organic compoundmaterial, it is necessary to consider a combination of a solvent inwhich the polymer organic compound material is dissolved and a memberconstituting an ink head. Actually, it is necessary to use a solventthat does not corrode the member constituting an ink head. However, theintermediate molecular weight organic compound dispersed in an aqueoussolution may be used, and thus, does not involve the above-describedproblem.

Note that the organic compound layer mentioned here indicates pixel rowspartitioned by partition walls 621, and the partition walls 621 areformed above the source wirings. That is, the row in which a pluralityof pixels are arranged in series along the source wiring is called theorganic compound layer. Incidentally, although the case in which thepartition walls 621 are formed above the source wirings is explainedhere, the partition walls 621 may be provided above the gate wirings. Inthis case, the row in which a plurality of pixels are arranged in seriesalong the gate wiring is called the organic compound layer.

Therefore, the pixel region 611 is regarded as the aggregate of aplurality of organic compound layers partitioned by stripe-shapedpartition walls provided above a plurality of source wirings or aplurality of gate wirings. In such a case, it can also be said that thepixel region 611 is composed of the organic compound layer in which astripe-shaped light emitting layer for emitting red light is formed, theorganic compound layer in which a stripe-shaped light emitting layer foremitting green light is formed, and the organic compound layer in whicha stripe-shaped light emitting layer for emitting blue light is formed.

Further, since the stripe-shaped partition walls are provided above theplurality of source wirings or the plurality of gate wirings, the pixelregion can be substantially regarded as the aggregate of a plurality oforganic compound layers divided by the plurality of source wirings orthe plurality of gate wirings.

FIG. 6 shows an example in which an organic compound (strictly speaking,mixture) is collectively applied to all the organic compound layersformed in the pixel region. That is, a head portion 601 is attached withthe same number of nozzles as the organic compound layers. With thisstructure, application can be performed to all the organic compoundlayers with one scanning to improve throughput remarkably.

Further, the pixel region may be divided into a plurality of zones, andthe head portion, provided with the same number of nozzles as theorganic compound layers included in one zone, may be used. That is,assuming that the pixel region is divided into n zones, the organiccompound material (strictly speaking, mixture) can be applied to all theorganic compound layers by scanning n times. In actuality, there is acase where a pixel size is small, for example, several tens of μm, andthus, the width of the organic compound layer may be approximatelyseveral tens of μm. In such a case, since it is difficult that thenozzles are arranged in a row, it is necessary to contrive thearrangement of the nozzles.

Embodiment 2

FIG. 7 schematically shows another example in which a polymer organiccompound layer 614 is formed so as to correspond to a pixel region byusing an ink jet printing device according to the present invention on asubstrate on which one electrode of an organic light emitting element isformed. In FIG. 7, the same parts as those in FIG. 6 are indicated bythe common reference numerals, and are not described here. FIG. 7 showsan embodiment in which application is conducted for each color, and onekind of the mixture is discharged from the ink head. In this case, therespective ink heads filled with the mixture for a red light emittinglayer, the mixture for a green light emitting layer, and the mixture fora blue light emitting layer are provided, and application is conductedfor each of the colors. Therefore, a thickness, a burning polymerizationtemperature in the later stage, and the like can be adjusted at theoptimum level for each color.

Embodiment 3

FIG. 8 shows an embodiment in which the printing device of the presentinvention is applied to a panel portion formed on a large-area substrate(mother glass substrate). On a mother glass substrate 800, panels 801 ato 801 f each including a pixel region with the same structure as thatin FIG. 6 are formed. Although two ink heads 802 a and 802 b are shownin FIG. 8, the number of ink heads can be arbitrarily set. In the casewhere the mixture is applied continuously over the adjacent pixelregions, the first and second piezoelectric elements are incorporatedinto the ink head and the timings for causing displacement aresynchronized, whereby the mixture can be discharged continuously or thedischarge can be stopped instantaneously, as described using FIGS. 3Aand 3B and FIG. 4. Accordingly, the organic compound layer can be formedat high speed with respect to the large-area substrate on which a largenumber of pixel regions are formed.

Embodiment 4

FIG. 9 shows an example of a manufacturing device of a light emittingdevice, which is incorporated with a printing device according to thepresent invention. In FIG. 9, a plurality of printing chambers 906 to908, a drying chamber 903, a load chamber 901, and an unload chamber 902are provided, and these are coupled by common chambers 904 and 909. Anintermediate chamber 905 couples the common chambers 904 and 909.Conveyance of a substrate is conducted by conveying means 910 and 911.The printing chambers 906 to 908 are respectively provided with inkheads 915 to 917 each comprising the structure as FIG. 1 or 2.

The load chamber 901 and the unload chamber 902 respectively havecassettes 912 and 913 for holding a substrate. The drying chamber 903 isprovided with a substrate stage incorporated with a sheathed heater, alamp light source, or a heating means using warm air 914, which can heatand dry the substrate after printing.

The respective chambers are partitioned by gate valves 920 a to 920 h.Thus, printing is conducted in an inert gas or in the same kind ofsolvent atmosphere as the mixture, whereby impurity contamination can beprevented. A printing method does not require vacuum, and thus has acharacteristic that the device structure becomes simple without vacuumpump, an airtight seal or the like.

FIG. 10 shows a structure of a device that enables continuous formationuntil forming an electrode of an organic light emitting element or apassivation film. Printing chambers 705 to 707 are respectively providedwith ink heads 720 to 722 each comprising the same structure as that inFIG. 1 or 2. Cleaning of the substrate before printing is conducted in acleaning chamber 702, and a cleaning means 718 conducts spin cleaning,brush cleaning or the like. A chemicals supply means 719 supplies analkaline or acid cleaning fluid. The cleaning means 718 may also adoptUV cleaning using ultraviolet light. Conveyance of a substrate isconducted by conveying means 714 to 716.

Various kinds of processing are performed at an atmospheric pressure ina load chamber 701, the cleaning chamber 702, the printing chambers 705to 707, common chambers 703, 708, and an intermediate chamber 704. Onthe other hand, processing is conducted under a reduced pressure in filmforming chambers 710, 711 for forming a film, which are provided withexhaust means 724, 727, respectively. As the exhaust means, a dry pump,an oil rotary pump, a turbo molecular pump, a cryo pump, a mechanicalbooster pump or the like is applied. Therefore, an intermediate chamber709, and an unload chamber 712 for temporarily holding the substrateafter film formation are similarly provided with exhaust means 723 and730. The respective chambers are partitioned by gate valves 700 a to 700l.

The film forming chamber 710 conducts film formation of a conductivefilm by an evaporation method, and is provided with an evaporationsource 726, a heating means 725 thereof and the like. The film formingchamber 711 is provided in order to form a film such as a siliconnitride film or a diamond-like carbon film by using a plasma CVD method.Therefore, the film forming chamber 711 is provided with a gas supplymeans 729, a glow discharge generation means 728 and the like. After anelectrode is formed on an organic compound layer, a passivation film canbe formed in succession. Thus, impurities can be prevented from mixingwith the organic compound layer.

Embodiment 5

FIG. 11 is a top view of an example of a structure of a pixel in anactive matrix drive light emitting device. Further, FIG. 12 is asectional view taken along a line A-A′ in FIG. 11. In both the figures,the pixel structure is described using common reference numerals.

In the pixel structure, two TFTs are provided in one pixel, one of theTFTs is an n-channel TFT 1204 for conducting a switching operation, andthe other is a p-channel TFT 1205 for controlling an electric currentthat is made to flow through an organic light emitting element. A wiring1105 is a signal line based on image data, and a wiring 1107 is a powersource supply line for supplying an electric current to an organic lightemitting element. Of course, when the present invention is applied,there is no limitation on the number of TFTs provided in one pixel, andan appropriate circuit structure may be adopted in accordance with adrive system of a light emitting device.

As shown in FIG. 12, an organic light emitting element 1174 isconstituted of a first electrode 1146, an organic compound layer 1171and a second electrode 1172. The first electrode and the secondelectrode can be distinguished into an anode and a cathode in accordancewith the polarity. A material with a high work function such as indiumoxide, tin oxide or zinc oxide is used as a material for forming theanode. A material with a low work function, which is comprised of alkalimetal or alkaline earth metal such as MgAg, AlMg, Ca, Mg, Li, AlLi orAlLiAg, typically a magnesium compound is used for the cathode.

A passivation film 1173 is formed thereon. The passivation film isformed by using a material which has a high barrier property againstoxygen and vapor, such as silicon nitride, silicon oxynitride ordiamond-like carbon.

In the p-channel TFT 1205 and the n-channel TFT 1204, active layers 1116and 1117 each comprising a channel forming region, source and drainregions, an LDD region and the like are formed, are formed of apolycrystalline semiconductor film. While first gate electrodes 1133,11314 are formed through a gate insulating film 1118, second gateelectrodes 1106, 1108 opposing the first gate electrodes with the activelayer therebetween are provided through insulating films 1110, 1111.Interlayer insulating films 1143, 1144 are formed by a combination of aninorganic insulating film and an organic insulating film.

The first electrode 1146 of the organic light emitting element isconnected with an electrode 1153 of the p-channel TFT 1205. A partitionwall 1170 is formed in order to separate adjacent pixels from eachother, and partition the pixels so that a mixture does not extend to theadjacent pixel when an organic compound layer is formed by an ink jetmethod. The partition wall 1170 is formed from a photosensitive orthermosetting resin material such as polyimide or acrylic so as to coveran end portion of the first electrode. The organic compound layer may beformed in a longitudinal direction or a horizontal direction.

The organic compound layer is formed in succession between a pair ofpartition walls by using an ink jet printing device. The ink head withthe structure shown in FIG. 1 or 2 is used.

In the case where the organic compound layer is formed in thelongitudinal direction, the arrangement shown in FIG. 14A is obtained.In the case where the organic compound layer is formed in the horizontaldirection, the arrangement shown in FIG. 14B is obtained. In FIG. 14A,reference numeral 1401 indicates a stripe-shaped partition wall formedin the longitudinal direction, 1402 a indicates an organic compoundlayer for emitting red light, and 1402 b indicates an organic compoundlayer for emitting green light. Of course, an organic compound layer foremitting blue light (not shown) is formed adjacently with the organiccompound layer for emitting green light 1402 b. Note that the partitionwall 1401 is formed above and along a source wiring through aninsulating film.

At this time, a distance D between pixels 1403 indicated by dotted linesis desirably five times of a thickness (t) of the organic compound layeror more (preferably, ten times or more). This is because the problem ofcrosstalk between the pixels may arise with D<5t. Incidentally, ahigh-definition image can not be obtained when the distance D is toolong, and thus, 5t<D<50t (preferably, 10t<D<35t) is preferable. Further,in FIG. 14B, reference numeral 1404 indicates a stripe-shaped partitionwall formed in the horizontal direction. 1405 a indicates an organiccompound layer for emitting red light, 1405 b indicates an organiccompound layer for emitting green light, and 1405 c indicates an organiccompound layer for emitting blue light. Incidentally, the partition wall1404 is formed above and along a gate wiring through an insulating film.In this case as well, a distance D between pixels 1406 indicated bydotted lines is preferably five times of the thickness t of the organiccompound layer or more (preferably, 10 times or more), and morepreferably 5t<D<50t (preferably, 10t<D<35t).

Embodiment 6

In this embodiment, FIGS. 13A and 13B show an example in which a lightemitting device provided with an organic light emitting element ismanufactured. FIG. 13A is a top view of the light emitting device, andFIG. 13B is a sectional view taken along a line A-A′ in FIG. 13A. On asubstrate 300 with an insulating surface (for example, a glasssubstrate, a crystalline glass substrate, or a plastic substrate), apixel region 302, a source side driver circuit 301, and a gate sidedriver circuit 303 are formed. Organic compound layers in the pixelregions are formed by using the ink jet printing device of the presentinvention in accordance with the above-described embodiments. Further,known TFTs and circuit technique may be applied to the driver circuits.

Reference numeral 318 indicates a sealing member, and 319) indicates aprotective film. The pixel portion and the driver circuits are coveredwith the sealing member 318, and the sealing member is covered withprotective film 319 and sealed by a cover member 320 using an adhesive.It is desirable that the cover member 320 is formed by using the samematerial as that for the substrate 300, for example, a glass substratein order to withstand deformation due to heat, external force, or thelike. The cover member 320 is processed to have a concave shape (with adepth of 3 to 10 μm) shown in FIG. 13B by sandblasting or the like. Itis desirable that the cover member 320 is further processed to form aconcave portion (with a depth of 50 to 200 μm) into which a drying agent321 can be arranged. Incidentally, reference numeral 308 indicates awiring for transmitting signals input to the source side driver circuit301 and the gate side driver circuit 303, and the wiring receives avideo signal and a clock signal from an FPC (flexible printed circuit)that is an external input terminal.

Next, the sectional structure is described with reference to FIG. 13B.An insulating film 310 is provided on the substrate 300, and the pixelregion 302 and the gate side driver circuit 303 are formed above theinsulating film 310. The pixel region 302 is constituted of a pluralityof pixels including a current control TFT 311 and one electrode 312 of alight emitting element electrically connected to a drain of the currentcontrol TFT 311. Further, the gate side driver circuit 303 is formed byusing a CMOS circuit in which an n-channel TFT 313 and a p-channel TFT314 are combined. These TFTs (including 311, 313, and 314) may bemanufactured in accordance with a known technique.

The pixel electrode 312 functions as an anode of an organic lightemitting element. Also, partition walls 315 are formed at both ends ofthe pixel electrode 312, and an organic compound layer 316 and a cathode317 of the organic light emitting element are formed on the electrode312 of the light emitting element. The organic compound layer 316 may beformed by freely combining a light emitting layer, a charge transportinglayer, a charge injecting layer, and the like.

For example, as described in Embodiment 1, a first organic compoundlayer comprised of PEDOT can be formed as a hole injecting layer, and asecond organic compound layer can be formed thereon by using the ink jetprinting device of the present invention. In this case, the secondorganic compound layer becomes a light emitting layer. A polymer orintermediate molecular weight organic compound material may be applied,and the specific example is shown in Embodiment 1.

The cathode 317 also functions as a common wiring to all the pixels, andis electrically connected to an FPC 309 through a connection wiring 308.Further, all the elements included in the pixel region 302 and in thegate side driver circuit 303 are covered by the cathode 317, the sealingmember 318 and the protective film 319. After the organic light emittingelement is completely covered by the sealing member 318, at least theprotective film 319 comprised of a diamond-like carbon (DLC) film or thelike is preferably provided on the surface (exposed surface) of thesealing member 318 as shown in FIGS. 13A and 13B. Also, the protectivefilm may be provided on the entire surface including the rear surface ofthe substrate. Here, attention has to be paid so that the protectivefilm is not formed at the part where the external input terminal (FPC)is provided. The protective film may not be formed there by using amask. Alternatively, the protective film may not be formed by coveringthe external input terminal portion with a masking tape.

The organic light emitting element is sealed by the sealing member 318and the protective film 319 with the above-described structure, wherebythe organic light emitting element can be completely shut from theoutside. Thus, substances that promote deterioration of the organiccompound layer due to oxidization, such as moisture and oxygen, can beprevented from entering the organic light emitting element. Therefore, alight emitting device with high reliability can be obtained. Inaddition, the structure may be adopted in which a pixel electrode is acathode, and an organic compound layer and an anode are laminated toprovide light emission in a reverse direction to that in FIG. 13B.

Embodiment 7

The light emitting device fabricated in accordance with the presentinvention is of the self-emission type, and thus exhibits more excellentrecognizability of the displayed image in a light place. Furthermore,the light emitting device has a wider viewing angle. Accordingly, thelight emitting device can be applied to a display portion in variouselectronic devices. For example, in order to view a TV program or thelike on a large-sized screen, the light emitting device in accordancewith the present invention can be used as a display portion for a TV sethaving a diagonal size of 30 inches or larger (typically 40 incheslarger) and an image monitor device (i.e., a display in which a lightemitting device is installed into a frame).

The image monitor device includes all kinds of displays to be used fordisplaying information, such as a display for a personal computer, adisplay for receiving a TV broadcasting program, a display foradvertisement display. Moreover, the light emitting device in accordancewith the present invention can be used as a display portion of othervarious electric devices.

Such electronic devices include a video camera, a digital camera, agoggles-type display (head mount display), a navigation system, a soundreproduction device (a car audio, an audio equipment, and the like), alap-top personal computer, a game machine, a portable informationterminal (a mobile computer, a portable telephone, a portable gamemachine, an electronic book, or the like), an image reproductionapparatus including a recording medium (more specifically, an apparatuswhich can reproduce a recording medium such as a digital video disc(DVD), and includes a display for displaying the reproduced image), orthe like. In particular, in the case of the portable informationterminal, use of the light emitting device is preferable, since theportable information terminal that is likely to be viewed from a tilteddirection is often required to have a wide viewing angle. FIGS. 15A to16B respectively show various specific examples of such electronicdevices.

FIG. 15A illustrates a TV set or an image monitor which includes a frame2001, a support table 2002, a display portion 2003, or the like. Thelight emitting device in accordance with the present invention isapplicable to the display portion 2003. The TV set or the image monitoris of the self-emission type and therefore requires no back light. Thus,the display portion thereof can have a thickness thinner than that ofthe liquid crystal display device.

FIG. 15B illustrates a video camera which includes a main body 2101, adisplay portion 2102, an audio input portion 2103, operation switches2104, a battery 2105, an image receiving portion 2106, or the like. Thelight emitting device in accordance with the present invention can beused as the display portion 2102.

FIG. 15C illustrates a portion (the right-half piece) of a display ofhead mount type, which includes a main body 2201, signal cables 2202, ahead mount band 2003, a display portion 2204, an optical system 2205, alight emitting device 2206, or the like. The light emitting device inaccordance with present invention is applicable to the display device2204.

FIG. 15D illustrates an image reproduction apparatus including arecording medium (more specifically, a DVD reproduction apparatus),which includes a main body 2301, a recording medium (a DVD or the like)2302, operation switches 2303, a display portion (a) 2304, anotherdisplay portion (b) 2305, or the like. The display portion (a) is usedmainly for displaying image information, while the display portion (b)is used mainly for displaying character information. The light emittingdevice in accordance with the present invention can be used as thesedisplay portions (a) and (b). The image reproduction apparatus includinga recording medium further includes a game machine or the like.

FIG. 15E illustrates a portable (mobile) computer which includes a mainbody 2401, a camera portion 2402, an image receiving portion 2403,operation switches 2404, a display portion 2405, or the like. The lightemitting device in accordance with the present invention can be used asthe display portion 2405.

FIG. 15F illustrates a personal computer which includes a main body2501, a frame 2502, a display portion 2503, a key board 2504, or thelike. The light emitting device in accordance with the present inventioncan be used as the display portion 2503.

The aforementioned electronic devices are more likely to be used fordisplay information distributed through a telecommunication path such asInternet, a CATV (cable television system) and the like, and inparticular likely to display moving picture information. The lightemitting device is suitable for displaying moving pictures since theorganic light emitting material can exhibit high response speed.However, if the contour between the pixels becomes unclear, the movingpictures as a whole cannot be clearly displayed. Since the lightemitting device in accordance with the present invention can make thecontour between the pixels clear, it is significantly advantageous toapply the light emitting device of the present invention to a displayportion of the electronic devices.

A portion of the light emitting device that is emitting light consumespower, so it is desirable to display information in such a manner thatthe light emitting portion therein becomes as small as possible.Accordingly, when the light emitting device is applied to a displayportion which mainly displays character information, e.g., a displayportion of a portable information terminal, and more particular, aportable telephone or a sound reproduction device, it is desirable todrive the light emitting device so that the character information isformed by a light emitting portion while a non-emission portioncorresponds to the background.

With now reference to FIG. 16A, a portable telephone is illustrated,which includes a main body 2601, an audio output portion 2602, an audioinput portion 2603, a display portion 2604, operation switches 2605, andan antenna 2606. The light emitting device in accordance with thepresent invention can be used as the display portion 2604. The displayportion 2604 can reduce power consumption of the portable telephone bydisplaying white-colored characters on a black-colored background.

FIG. 16B illustrates a sound reproduction device, a car audio equipmentin concrete term, which includes a main body 2701, a display portion2702, and operation switches 2703 and 2704. The light emitting device inaccordance with the present invention can be used as the display portion2702. Although the car audio equipment of the mount type is shown inthis embodiment, the present invention is also applicable to a portabletype and a domestic type sound reproduction device. The display portion2702 can reduce power consumption by displaying white-colored characterson a black-colored background, which is particularly advantageous forthe audio of the portable type.

As set forth above, the present invention can be applied variously to awide range of electronic devices in all fields.

As described above, in the printing device of the present invention, thefirst and second piezoelectric elements are incorporated into the inkhead, and the timings for causing displacement are synchronized. Thus,the mixture can be discharged continuously, and the discharge can bestopped instantaneously. Therefore, time for position control inprinting the organic compound layer is shortened, and the printing speedcan be increased.

Such printing device is applied for manufacturing the light emittingdevice, whereby processing time which is necessary for forming theorganic compound layer can be shortened. In particular, the printingdevice is appropriately applied to the production method in which aplurality of display panels are taken out from one large-area substrate.In the case where the plurality of pixel regions are provided in thelarge-area substrate, the discharge of the mixture is stoppedinstantaneously during the movement of the ink head between the pixelregions, whereby the ink head can be moved at higher speed to thelarge-area substrate. The second piezoelectric element is provided inorder to stop the discharge of the mixture instantaneously, whereby thehigh speed in printing can be realized.

1. A method for manufacturing a light emitting device comprising thesteps of: applying an organic compound from a discharge port of an inkhead, which comprises a first pressure generation chamber and a secondpressure generation chamber which are connected to each other andprovided with a first piezoelectric element and a second piezoelectricelement, respectively, into a pixel region by vibrating the firstpiezoelectric element, while the second piezoelectric element is keptinactivated; and stopping the application of the organic compound by thesteps comprising: stopping the vibration of the first piezoelectricelement; starting the vibration of the second piezoelectric elementafter stopping the vibration of the first piezoelectric element; andstopping the vibration of the second piezoelectric element, wherein theorganic compound is arranged to be supplied to the second pressuregeneration chamber from the first pressure generation chamber and thento be applied to the pixel region through the discharge port, andwherein the vibration of the first piezoelectric element and thevibration of the second piezoelectric element are arranged to change avolume of the first pressure generation chamber and a volume of thesecond pressure generation chamber, respectively.
 2. A method accordingto claim 1, wherein the organic compound is dispersed in an aqueoussolution.
 3. A method according to claim 1, wherein the organic compoundis tetrakis (2-mercapto-benzoxazolate) tungsten.
 4. A method accordingto claim 1, further comprising spraying a gas to the applied organiccompound through a nozzle which is provided to the ink head.
 5. A methodaccording to claim 1, wherein the first piezoelectric element isoperated at a higher oscillation frequency than the second piezoelectricelement.
 6. A method for manufacturing a light emitting devicecomprising the step of: forming a light emitting layer by applying asolution of an organic compound, wherein the application of the organiccompound is performed by the steps comprising: dropping the solution ofthe organic compound from a discharge port of an ink head, whichcomprises a first pressure generation chamber and a second pressuregeneration chamber which are connected to each other and provided with afirst piezoelectric element and a second piezoelectric element,respectively, by vibrating the first piezoelectric element, while thesecond piezoelectric element is kept inactivated; and stopping theapplication of the organic compound by the steps comprising; stoppingthe vibration of the first piezoelectric element; starting the vibrationof the second piezoelectric element; and stopping the vibration of thesecond piezoelectric element, wherein the solution of the organiccompound is arranged to be supplied to the second pressure generationchamber from the first pressure generation chamber and then to beapplied through the discharge port, and wherein the vibration of thefirst piezoelectric element and the vibration of the secondpiezoelectric element are arranged to change a volume of the firstpressure generation chamber and a volume of the second pressuregeneration chamber, respectively.
 7. A method according to claim 6,wherein the organic compound is tetrakis (2-mercapto-benzoxazolate)tungsten.
 8. A method according to claim 6, further comprising sprayinga gas to the applied solution of the organic compound through a nozzlewhich is provided to the ink head.
 9. A method according to claim 6,wherein the first piezoelectric element is operated at a higheroscillation frequency than the second piezoelectric element.
 10. Amethod for manufacturing a light emitting device comprising the step of:forming a light emitting layer by applying an aqueous dispersion of anorganic compound, wherein the application of the organic compound isperformed by the steps comprising: dropping the aqueous dispersion ofthe organic compound from a discharge port of an ink head, whichcomprises a first pressure generation chamber and a second pressuregeneration chamber which are connected to each other and provided with afirst piezoelectric element and a second piezoelectric element,respectively, by vibrating the first piezoelectric element, while thesecond piezoelectric element is kept inactivated; and stopping theapplication of the aqueous dispersion of the organic compound by thesteps comprising: stopping the vibration of the first piezoelectricelement; starting the vibration of the second piezoelectric element; andstopping the vibration of the second piezoelectric element, wherein theaqueous dispersion of the organic compound is arranged to be supplied tothe second pressure generation chamber from the first pressuregeneration chamber and then to be applied through the discharge port,and wherein the vibration of the first piezoelectric element and thevibration of the second piezoelectric element are arranged to change avolume of the first pressure generation chamber and a volume of thesecond pressure generation chamber, respectively.
 11. A method accordingto claim 10, wherein the organic compound is tetrakis(2-mercapto-benzoxazolate) tungsten.
 12. A method according to claim 10,further comprising spraying a gas to the applied aqueous dispersion ofthe organic compound through a nozzle which is provided to the ink head.13. A method according to claim 10, wherein the first piezoelectricelement is operated at a higher oscillation frequency than the secondpiezoelectric element.
 14. A method for manufacturing a light emittingdevice comprising the steps of: forming a first organic compound layerby an application method; and forming a light emitting layer by applyinga solution of a second organic compound on the first organic compoundlayer, wherein the application of the solution of the second organiccompound is performed by the steps comprising: dropping the solution ofthe second organic compound from a discharge port of an ink head, whichcomprises a first pressure generation chamber and a second pressuregeneration chamber which are connected to each other and provided with afirst piezoelectric element and a second piezoelectric element,respectively, by vibrating the first piezoelectric element, while thesecond piezoelectric element is kept inactivated; and stopping theapplication of the solution of the second organic compound by the stepscomprising: stopping the vibration of the first piezoelectric element;starting the vibration of the second piezoelectric element; and stoppingthe vibration of the second piezoelectric element, wherein the solutionof the second organic compound is arranged to be supplied to the secondpressure generation chamber from the first pressure generation chamberand then to be applied through the discharge port, and wherein thevibration of the first piezoelectric element and the vibration of thesecond piezoelectric element are arranged to change a volume of thefirst pressure generation chamber and a volume of the second pressuregeneration chamber, respectively.
 15. A method according to claim 14,wherein the first organic compound layer includes poly (3,4-ethylenedioxythiophene).
 16. A method according to claim 14, wherein the secondorganic compound is tetrakis (2-mercapto-benzoxazolate) tungsten.
 17. Amethod according to claim 14, further comprising spraying a gas to theapplied solution of the second organic compound through a nozzle whichis provided to the ink head.
 18. A method according to claim 14, whereinthe first piezoelectric element is operated at a higher oscillationfrequency than the second piezoelectric element.